[InstrProf] Report error when merging temporal profiles

[ellis]

Summary

Temporal profiles do not support profile merging at runtime. The reason
is that each function can only store one timestamp and the
llmv-profdata tool is responsible for sampling traces during the merge
command. Report an error in __llvm_profile_merge_from_buffer() if
merging a temporal profile.

The added test also checks that lightweight profiles throw an error,
although this may be fixed in https://reviews.llvm.org/D157632

[zequanwu]

LGTM.

compiler-rt/lib/profile/InstrProfilingMerge.c

int __llvm_profile_merge_from_buffer(const char *ProfileData,
                                      uint64_t ProfileSize) {
   if (__llvm_profile_get_version() & VARIANT_MASK_DBG_CORRELATE) {
     PROF_ERR(
         "%s\n",
         "Debug info correlation does not support profile merging at runtime. "
         "Instead, merge raw profiles using the llvm-profdata tool.");
     return 1;
   }
+  if (__llvm_profile_get_version() & VARIANT_MASK_TEMPORAL_PROF) {
+    PROF_ERR("%s\n",
+             "Temporal profiles do not support profile merging at runtime. "
+             "Instead, merge raw profiles using the llvm-profdata tool.");
+    return 1;
+  }
 
   __llvm_profile_data *SrcDataStart, *SrcDataEnd, *SrcData, *DstData;
   __llvm_profile_header *Header = (__llvm_profile_header *)ProfileData;
   char *SrcCountersStart;
   const char *SrcNameStart;
   const char *SrcValueProfDataStart, *SrcValueProfData;
   uintptr_t CountersDelta = Header->CountersDelta;
 

compiler-rt/test/profile/instrprof-merge-error.c

+// RUN: rm -rf %t; mkdir %t
+
+// RUN: %clang_pgogen -o %t/dbg -g -mllvm --debug-info-correlate -mllvm --disable-vp=true %s
+// RUN: env LLVM_PROFILE_FILE=%t/dbg_%m.profdata %run %t/dbg 2>&1 | count 0
+// RUN: env LLVM_PROFILE_FILE=%t/dbg_%m.profdata %run %t/dbg 2>&1 | FileCheck %s --check-prefix=DBG
+
+// DBG: Debug info correlation does not support profile merging at runtime.
+
+// RUN: %clang_pgogen -o %t/timeprof -mllvm -pgo-temporal-instrumentation %s
+// RUN: env LLVM_PROFILE_FILE=%t/timeprof_%m.profdata %run %t/timeprof 2>&1 | count 0
+// RUN: env LLVM_PROFILE_FILE=%t/timeprof_%m.profdata %run %t/timeprof 2>&1 | FileCheck %s --check-prefix=TIMEPROF
+
+// TIMEPROF: Temporal profiles do not support profile merging at runtime.
+
+int main() { return 0; }